The Serial Killer
by LucyMagnus
Summary: What will happen when Jo has to cooperate with her ex-husband Russ, who still loves her? Will Mac help Jo to solve this case from her past? Jo/Mac scenes in later chapters.
1. Chapter 1

**Hi, I'd like to say few things before you'll start to read my story. Firstly, English is not my mother language so I take every responsibility for any mistake you'll find. I tried hard to avoid mistakes but I think I didn't find all of them. So I appologize for them.**

**Secondly, I'm new to writing CSI: NY fanfic. I'll try hard to make this story interesting for you.**

**Last thing, please review this chapter. I'll post new one only when I'll see that someone actually reads this. Otherwise I don't see a point of writting a story when nobody reads it.**

**Thank you for reading my babbling and now here we go. Enjoy!**

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When Jo Danville has been looking back to the beginning of the day, she knew everything went too well so she should expecting that problems would come. But in the morning she was just grateful that the prep Dan caught wasn't making any fuss and after he has seen they knew almost everything he had done, he confessed that he done it. It was really so easy but on other hand Jo had many evidence they prooved that it was him who hurt badly the shop assistant in the small shop with alcohol and tabac.

After the prep confessed his crime, all Jo had to do was put toghether all evidence, wrote report about this crime and make sure everything would be ready for a court. Every evidence had to have filled every information needed to show to the jury. And the final report had to have Mac signature because he was the head of this crime lab.

Jo knew the process and even though she didn't like paper work, she was glad they caught the bad guy and put him where he belonged. She had this case for herself because everyone else had full hands of different cases. Mac trusted her abilities to do this case alone. Jo did everything to show her boss and more her friend that she deserved his trust. She had the help of one of the best detectives whom she prefered to work, Don Flack. They made good team together so they caught the prep quickly.

Jo was almost finished with every paper work that had to be done when the door to her office opened. She looked up from the mess on her desk where she tried to find one paper and she was still failing. Through the door came in Mac Taylor. Jo smiled at him when she saw he was shaking his head. Jo knew Mac couldn't understand why she had to have such a mess on her table but at least he stopped asking her how she could find anything she was looking for.

"What's going on, Mac?" Jo asked. "Do you need my report already?"

Mac looked at her then he sat down on the opposite site of her desk.

"Don called. We have another case and you're the only one who doesn't have any case. But there is one problem. FBI will be looking over our shoulder because it seems this case has to do with something they have been working on for some time. The FBI team here is leading by your exhusband Russ. Would it be a problem for you to cooperate with him?"

Jo sighed. It seemed that it didn't matter she left the FBI and got divorced with Russ because she had to deal with him and the bureau anyway. She knew when she would say this could be a problem, Mac would try to put someone else on this case and Jo would take the case they were working on. But that would be complicated and she didn't want to make things for Mac complicated. She knew they were already complicated enough because of the cooperation with FBI. It wasn't that they didn't like the people working for the bureau, at least not most of the time. But they had different methods of investigating and interogating suspects and Mac with others didn't like it.

"That won't be a problem, don't worry Mac," Jo said finally and smiled at him with smile she hoped was reassuring.

"Fine,"Mac answered. "I don't have much information but I'm sure Don will tell you everything you need to know and Russ probably will tell you even the things you don't need to know." Then he gave her the address where she had to go to. After that he wished her good luck and left her office.

Jo sighed, she really wasn't looking forwad to working this case because of the coopeartion with Russ but she knew she couldn't leave Don on the crime scene alone. She looked around her desk and with small smile she finally found the paper she was looking for when Mac interupted her. It was the last paper for her final report to the previous case. She put it together because she meant to give it to Mac on her way to new case. Then she took everything she needed and with the report for Mac left her office.

XXXXXX

The first person who Jo saw when she entered the buliding where the crime has been commited was her exhusband Russ. Jo hoped she would have the chance to speak with Don first but this time she wasn't so lucky. She wanted to know first what exactly happened, to know how many victims were here and so on but now she had to go pass Russ and she knew she wouldn't be able to pass him without any talk.

"Russ, before you start asking me any questions I wasn't on the crime scene so I'm not able to tell you anything just yet." Jo said briskly.

Russ blinked but then he smiled at her. "I just wanted to say hello and to remind you I need to know whatever you'll find, okey? You worked on this case, too, before you left the bureau so I'm sure I don't need to remind you what's at the stake."

When Russ saw Jo's furrowed forhead he explained to her that in one of the flats in this building were four killed teenage girls who were stabbed to death and had slit throat. Brother of one of the girls found them and called police who then called crime lab and FBI. Brother still didn't say a thing because he was in a shock.

Jo's eyes widdened when she was listening to Russ. They really had a case few years ago what had some similarity with this one. But she still wasn't inside the flat and she didn't see the crime on her own so she couldn't make any state about it.

But the case Russ was talking about wasn't closed yet. They weren't able to catch the prep even though FBI had every possible equipment they could think about. Those killings have started some time ago in Trenton, New Jersey, then it stoped before local police could catch the killer. After year and half same killings started in Washington where Jo was working with Russ and others and tried to catch the killer. They were cooperating with police but because the same pattern was seen in Trenton, FBI was working on the case too. The bureau wasn't any luckier than police and after seven dead teenage-girls the killing stoped as sudden as in Trenton.

"We don't know yet if the death of those girls have anything to do with the Trenton killer." Jo objected. She mentioned the nickname that was given to the monster by news in New Jersey. By then police didn't call it by any name so they started to use this name and FBI was continuing using it.

"Go upstairs and look at it then you'll agree with me." Russ answered and showed with his right arm the shortest way to the elevator.

Jo looked at him then she looked the direction Russ was poining at. She decided to do what he was suggesting. She had to go to the flat anyway but right now she wasn't looking forward to doing so. It wasn't as if she was enjoying to going to the crime scene but this time, if Russ was right, she already knew what was waiting for her and she was sure she would be thinking about Ellie, her daughter, all the time she would be working on the crime scene.

Jo took the elevator and got out at the 17th floor. When the door of the elevator opened she already knew what way she needed to go. She couldn't miss the police officers, coroner, people who would take the dead girls to the pathology and many others. She went stright to the opened door and showed her badge to the officer standing next to the door. Then she ducked under the tape which said DO NOT CROSS and suddenly she was looking at the crime scene.

There, in the living room all the hell was broken. For dead bodies were lying in different position. One was close to the door leading from living room to the corridor, second was still half sitting half lying on the couch, third one was lying on her back over coffe table what wasn't standing on its usual spot. Last victim was behind the couch as if she was trying to hide herself but failed.

"Oh my God," Jo said when she saw it. Just from the first look Jo wanted to agree with Russ because it looked so familiar. But she had to trust the evidence not her feelings. At least that was what Mac Taylor was always saying and Jo had to agree with him.

So Jo tried to stop thinking about the similarities with previous killings and started to concentrate on this case. She wanted to take it as if this was completely new and different case so her feelings won't play any tricks with her. She took a deep breath, put her silver case on the floor, picked her camera up and started to work.

Jo hoped Mac would give her another team member to help her as soon as possible. Although she didn't mind to work alone, this case would be big and it would be useful to have someone who would help her. It was something different to work on a case with one dead or on a case with four dead people alone.


	2. Chapter 2

**I would like to thank every single one of you who read my first chapter. Big thank is for the people who wrote me review.**

**Special thanks for csinyfan28 because it's her fault I'm writing this story. :-) I'm greateful you encouraged me.**

**And again, I'm appologizing for every mistake you'll find. **

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Jo had worked for hours on the crime scene. She was on her own so it took longer then it would take if she had another member of the team. She had to took pictures of everything, picked up every evidence, looked for finger prints, took samples of blood and other important things. It was time-consuming task but Jo knew she had to do it properly because even little pice of evidence could lead her to the killer. And this time she wanted to do everything to catch this bastard and put him behind the bars where he should be years ago.

Even when the bodies were taken to the coroner, Jo could see them in front of her inner eye. Time to time she had to shake her head to stop thinking about the young girls whose life ended so soon and so abruptly. Jo was happy Ellie didn't have any intention going to parties just yet but she knew that sooner or later even she would have to deal with the problem if she would allowed Ellie to join some parties.

When Jo finished her work, she packed everything up and put it into her car. But before she left the crime scene, she came up to the boy who found the girls. Doctor already check him up and said that the boy was in shock and needed some time to deal with the events of this day. In other case Jo would leave him alone but she really needed to know identities of the other girls because they didn't have any ID.

Jo went to the kitchen and waved the cop, who were there with the boy, away. Then she made a cup of tea and put it in front of the boy. She sat up and looked at him.

"Hi, I'm Jo. I'm so sorry what happened to your sister and I promise I'll do everything I can to find the one who's done it. But I would like to ask you for help. Could you tell me names of the other girls, please?"

The boy looked up at her but said nothing. He even didn't have touch the cup. Jo sighed slightly. She really didn't want to press on him but she didn't have any choice.

"You think you could prevent what happened tonight, right? You're thinking that you're the older brother who should protect his little sister, am I right?"

Finally the boy looked up at her but when she saw the pain in his eyes her heart skipped a beat. His eyes were full of pain what shouldn't be there. This boy should have had nice teenage life without concerns of adults life. But today's night had changed everything. Jo knew this boy will remember this day for the rest of his life.

"May I say you something?" Jo asked politely and without waiting for an answer, she continued: "I'm sure your sister asked you to leave for tonight and let her have here a party. And because you're a good brother you left. You wouldn't be able to protect all of the girls and maybe you would end up dead. But you can help me to get him behind bars. Will you do that? Not for me but for your sister."

Suddenly all the feelings the boy was keeping inside made him cry. Tears were silently falling down on his cheeks and he was shaking. Jo caught his hand and sqeezed it slightly. She knew this was difficult for him but it was better than keeping the feelings inside.

The boy confirmed everything what Jo said. His sister wanted to use the opportunity that their parents were gone and make small party for her best friends. Thomas, the brother, stayed at his friend's flat but returned to check up on the girls to make sure they were all right. The door of the flat was open and he found all girls dead. Then he gave Jo names of the other girls with their address and phone number to his parents who still didn't know about the death of their daughter.

When Jo finally left the flat she spot Russ standing next to her car. She was surprised to see him here but she still continued to her car, not looking at him. She loved him once but that was some time ago. She knew Russ wasn't bad guy, she actually still liked him but not enough to be with him again. Russ was great father to Tyler and that was all what mattered now when it came to it.

"So, do you still think that it's not the Trenton case?" Russ asked her when she came close enough that he didn't have to speak loud.

"Give me a break, Russ. I've been for ages in the flat, I haven't eaten almost whole day. Before I'll tell you anything else I need to speak with our coroner and look through the evidence. You know me, I won't give you any statement before I know the facts."

Russ threw arms in the air in defending gesture. "Alright. But do you have anything I can work with? You know we're supposed to cooperate, so give me something and I let you be for a while."

Jo sighed. She knew him very well and knew how he could be stubborn. "Fine. I'll give you addresses of the parents of the dead girls. You can talk to them and tell them what happened. I have phone number of the parents of the boy. He said they're still out of town, so you should call them and tell them to come back home as soon as possible."

Jo watched Russ closing his eyes. She knew how much he hated this part of his job but he knew the right questions to ask and it would help them to proof if this was the Trenton case or not. And to be honest, she didn't like this part of their job too so she was glad she didn't have to do it.

Russ run hand through his hair. "Alright Jo, I'll do that but you owe me at least a coffee if not lunch." He smiled at her and then finally left.

XXXXX

Jo was working on the clothes of the girls but her thoughts were somewhere else. She was thinking about the part of the Trenton case she has been working on back in Washingon. She was angry at herself and all her co-workers because they weren't able to catch this killer. Jo was wondering how many young girls have to die before they will be able to put him behind the bars.

Mac was standing in the door frame and was watching Jo for a while. She didn't know he was there, that was unlike her. He was sure she wasn't paying much attention to her work right now. After another half a minute he decided to walk in.

"Jo," he said with still voice because he didn't want to spook her by his sudden interruption of her thoughts, but he still saw her to jump slightly when she heard him. "We should talk."

Jo looked at him, wondering how long was he watching her, because she knew she didn't pay attention to her work. She hoped he would let her to work on this case because she really wanted to catch this guy. But right now she didn't do anything to convince Mac to let her stay on this case.

'Where?" She asked simply and put all the evidence on the table.

"In my office."

Mac let Jo walk first into his office then he closed the door for privacy. He stoped Jo before she sat down in front his desk and pointed on the couch. Jo looked at him curiously but without asking for explanation she sat on the couch while watching Mac sitting next to her.

"There is something you are not telling me. The case means for you more than any usual we worked on. Does it have to do anything with Russ?" Mac asked her.

Jo sighed. She knew Mac was good detective and would figure it out but she didn't expect that it would be so soon. She didn't have prepared anything to tell him to make it like there wasn't anything special what kept her on this case. But the truth was she had great reason to working on this case. She just was afraid Mac wouldn't let her working on it as soon as he would know the truth. Right now Jo didn't have any choice than to be honest with Mac and hope he would understand.

"There were so many girls he murdered, Mac. They weren't much older than Ellie and I've done everything I could to catch him in Washington. But he was really good. We didn't know how he looked like, we didn't have any fingerprint, any DNA. Nothing. It was frustrated. Seven dead girls and we weren't any closer to catch him than police in Trenton. When the killings stopped they didn't let us continue searching for him. They told us we had different cases to work on."

Mac saw how much Jo was frustrated that she didn't have the opportunity to search and find the killer but he felt like there was something more she wasn't telling him. He was thinking hard to figure it out. He knew Jo well and she was behaving differently than usually. Suddenly something came on his mind.

"How old was Ellie's friend when he murdered her?" Mac asked her.

Jo gave him startled look. He found the truth out. She was emotionally involved in this case and Mac wouldn't let her continue.

"Mac, please,"she didn't want to plead, that wasn't something she usually did but this time she was desperate.

Mac looked at her. "Tell me the truth, then we'll see what we can do about it, alright?"

Jo nodded because she knew she didn't have any choice than tell him everything.

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**Thank you for reading. I would be greatful if you could write me review.**


	3. Chapter 3

**I would like to thank to Quille and csinyfan28 for their amazing support and awesome reviews. I'm always happy to read your reviews.**

**Again, I'm sorry for all the mistakes you'll find. But nobody is perfect, right? :-)**

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Jo took a moment to gather her thoughts before she started to speak. Then she told Mac everything. Back at the FBI they were working day and night when the first killing hit Washington. But they couldn't find anything. It looked like the killer knew well what to do not to leave any trace behind. Even though on this case were working people from Washington police and FBI, they weren't more successful than Trenton police before.

"It was crazy time because he was killing young girls. Everyone was pushing hard on us to catch him. I was single mom with two kids to take care of and to handle this case. It wasn't easy but Ellie and Tyler were amazing. Tyler helped me with Ellie and she found new friend, Melisa. She was few years older than her but it seemed they understood each other well. Melisa was very friendly and kind girl."

Jo felt silent for few moments but Mac didn't say anything. He knew how hard it must be for Jo to rememer everything, even though he was sure she was thinking about this since she found out that this case is related to the Trenton one.

After a moment of silent Jo continued. One Saturday morning woke her up a call from Russ. He was already on the crime scene. When Jo arrived and saw Melisa, she felt terrible. Apart from the fact that she was young girl, she was also Ellie's friend and above all Jo knew her, so that ment she wasn't supposed to work on this case. But she didn't tell anyone she knew the girl. More than ever she wanted to catch him. She owed it not only to all the families but more importantly to her daughter and she didn't want to dissapoint her.

"But when the killings stopped they told us to let it be. Can you understand it? How we were supposed to let it be? To tell parents of their dead daughter that we won't catch him? How could I tell this to Ellie?" Jo was frustrated and she had to gather all her strength not to speak loud.

Mac sighed. He had to do a big decision now. Jo wasn't supposed to work on this case because she was emotionaly involved, on the other hand she knew about this case more than any other team member. Mac was thinking what decision would be the best. When Jo would continue working on this case and their boss would find out, both of them would have a big problem. But he wanted to solve this case as much as Jo.

"Is there anyone who knows that you knew this Melisa?" Mac asked her finally.

"Nobody, Mac. Well, only Ellie and now you. I haven't even told Russ about it," Jo assured him.

"Could anyone find out that you knew her?"

"Ellie and Melisa weren't at the same class. Someone has to know the two knew each other and to proove I knew Melisa well enough to be emotionaly affected. It's almost impossible."

Mac fell silent for a moment. He actually didn't have to ask those questions because he already made a decision, he just wanted to be sure it was the right decision.

"I will let you work on it but you need to inform me about everything, alright? When I will see your feelings are affecting the work I will need to take you off this case. Are we clear?"

"Crystal clear, Mac," Jo assured him with smile. "Thank you so much. I promise you won't regret you left me on this case."

She sqeezed his arm thankfully and left his office ready to continue on the evidence that was waiting for her. Mac was looking at the door what closed behind Jo and rubbed his forhead. He liked Jo and was wondering if it had clouded his judgement.

XXXXX

Russ interogated all the families but he didn't hear anything what could help him. Nobody knew anything and that made him frustrated because it reminded him so much of the case he was working on in Washington. He has hated it before and he hated it now too. When they told him to stop working on the case it made him furious. Now he swore to himself he would do everything he could to finally catch this bastard.

He remembered how frustrated and furious looked Jo when they told them to stop investigate this case in Washington. Now they were working on it together again. He saw in her eyes that she was determined to solve this case as much as him. Russ hoped that this time they would be successful.

After interogating Melisa's parents and her sister, he had some feeling beyond description. He was sure Melisa's younger sister Danielle knew something but she didn't want to speak about it in front of her parents. Maybe she even didn't want to tell him because he was a guy. It wouldn't be for the first time this happened to him. Russ knew there was only one thing he could do. Ask Jo for help the next day. Not only that she knew how to handle kids and teenagers but she also had a daughter in Danielle's age.

XXXXX

Jo has been working on the evidence when Russ came up to her. She still felt a bit unconfortable when she had to work with him, but she remembered she promised to Mac it wouldn't be a problem to cooperate with Russ so she did the best not to show anything about her feelings.

"Jo, I need your help," Russ said when he came into the lab.

'What's going on?" Jo asked and put an evidence she was holing in her hands on the table.

Russ explained her about his feelings he had when he interogated Danielle. He told Jo everything he could, hoping she would agree to help him and interogate Danielle again. Russ was sure Danielle was holding something back.

Jo run her hand through her hair. Russ didn't have to persuade her, she wanted to help him. On the other hand she needed to work on the evidence too. She really hoped Mac would give her another team member but it looked like everyone else was too busy to work with her.

"You help me and I'll help you. In return for your help you can send the evidence to bureau's lab," Russ said when he saw her face.

Before Jo had the opportunity to answer sombody knocked on the door to the lab. Jo looked behind Russ' back and saw Mac coming through the door.

"Do you have any problem, Jo?" Mac asked her.

Jo explained him that she was working on the case alone and she needed help because the case was huge and she couldn't do everything at the same time. Jo told him she wanted to interogate Danielle but at the same time she wanted to continue on the evidence and she didn't want to send the evidence to the bureau's lab even through she should cooperate with the FBI.

"Go and talk to Danielle, I will be working on the evidence. I finished everything I had to do and now I'm free to help you," Mac said.

Jo smiled at him. Mac just saved her. Now she could help Russ without sending the evidence to the bureau. And above all of it she would be coopearting with Mac.

"Alright Russ, lead the way and show me where Danielle lives. I will do my best to get from her everything she's holding back," Jo said with excitement.

Mac was glad he could help Jo. He always liked when he saw her smiling and was glad when he was the reason what makes her smile. Luckily he finished everything he was working on and he didn't have another case to work on. He decided to help Jo because he knew her case was huge and she wouldn't be able to do all the work alone. Even Russ' help couldn't be enough. Besides he wanted to be sure it wasn't difficult for Jo to coopeate with her ex-husband.

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**Thanks for reading. I would be really grateful if you could write a review.**


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